Anne Hathaway dropped 16 pounds on a detox diet for her role in Les Miserables.

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Natlie Portman lost 20 pounds for her Black Swan role as a ballerina.

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Mila Kunis also dropped 20 pounds for her ballerina role in Black Swan â she got down to just 98 pounds.

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Matt Damon lost 40 pounds to play an army medic in Courage Under Fire in 1996.

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For his role in The Informant, Matt Damon put on 30 pounds to play a CIA-informant. He told âEWâ that on top of meals on set, he would also eat McDonaldâs and a bag of Doritos!

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Seth Rogan lost 40 pounds for his role in The Green Hornet.

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Renee Zellweeger made her weight go up and down for a few movie roles. She gained and then lost 20 pounds for Bridget Joneâs Diary and Chicago, and then gained back the weight for Bridget Jones: The Edge of Reason.

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George Clooney gained 30 pounds for his role as a CIA operative in the movie Syriana.